A Greenhouse
In Montreal

Michel Leonard, president of Canadian publicly traded landlord BTB Real Estate Investment Trust, has been seeking to transform an industrial building in Montreal into trendy office space for designers. Last year, two entrepreneurs approached him with a way that might help make that happen: They wanted to build a greenhouse on his roof.

Today, a company called Lufa Farms is two to four weeks away from finishing construction on a 31,000-square-foot commercial greenhouse on top of Mr. Leonard's two-story building. Lufa has signed...